U-tube for vacuum gauges and the like



Feb. 24, 1931. WQQLLEY 1,794,268

U-TUBE FOR VACUUM GAUGES AND THE LIKE Filed Sept. 15 192 Liouid Levei.

Inventor: Raw E, \A/ooHe His flttovnay.

Patented F eh. 24, 1931 UNITED STATES PATENT oFFicE REW E. WOOLLEY, 0FSGHENECTADY, NEW YORK, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO BAILEY METERCOMPANY, A CORPORATION OF DELAWARE U-TUBE FOR VACUUM GAUGES AND THE LIKEApplication filed September 15, 1924. Serial No. 737,956.

10 stood, however, that this is only by way of example and that myinvention may be utilized wherever found applicable.

For a consideration of what I believe to be novel and my invention,attention is di- 15 rected to the accompanying description and theclaims appendedthereto.

In the drawing, the figure is a diagrammatic view of a vacuum gaugeembodying my invention. 7

Referring to the drawing, 1 indicates a base or pedestal comprising avertical tube 2 upon the top of which is mounted a casing 3. Casing 3 isclosed by a cover plate 4. Mounted inside of easing 3 is a transformercore 5, comprising three legs, the two outer legs being mounted invertical grooves 6 in casing 8. On the middle leg is arranged a primarywinding 7, which is embedded in a cylinder 7 a of suitable insulatingmaterial and which at one end is grounded on casing 3, as is indicatedat 8. The other end of primary winding 7 projects out through aninsulating bushing 9 in cover plate 4, and is connected to one terminalof the transformer winding 10 the other terminal of which is grounded oncasing 3, as is indicated at 11. Transformer winding 10 forms thesecondary winding of a stepdown transformer which has its primarywinding 12 connected by conductors 18, 14 to a source of alternatingcurrent of constant potential indicated by the lead wires 15. Primarywinding 7' is thus connected to a source of alternating current 15through the intermediary of the stepdown transformer comprising windings10 and 12. It is desirable that a voltage of comparatively small valuebe impressed on winding 7 while the voltage ordinarily met with is ofthe order of 110 volts or more, and the purpose of the stepdowntransformeris to provide a voltage for winding 7 of suitable value. I

Connected to the bottom of easing 3 is a pipe 16, which is located intube 2 and pro jects down a suitable distance, and at its lower end isconnected to the lower end of a vertical pipe or well 17 of relativelylarge diameter, which is supported by a bracket 17*. Connected to thetop of pipe or well 17 is a pipe 18 of relatively small diameter whichextends up to a point somewhat above the bplttom of casing 2, and isopen to the atmosp ere.

Casing 3 and pipe16'form one leg of a U-tube, the other leg of which isformed by pipes 17 and 18, which may be considered as a single pipehaving sections of difierent diameters. This U-tube is filled with aliquid, such as mercury, which is a conductor of electricity, up to alevel such that the mercury forms a ring around the lower end of themiddle leg of the trzinsformer-core, as is indicated at 19. This is theliquid level indicated in the drawing and represents zero vacuum.

The mercury ring 19 around the middle leg of the transformer core formsa closed secondary winding of a single turn for the transformercomprising core 5 and winding 7, the resistance of which varies inaccordance with the depth of the mercury ring. The current flowing inprimary winding 7 will be proportional to the resistance of thesecondary winding formed by the mercury ring so that as the mercuryrises and falls in casing 3 the current flowing in primary winding 7 andhence in the circuit comprising lead wires 13and 14: will vary in accordance with the depth of the mercury ring. In the circuit comprising leadwires 13 and 1e are suitable electrical measuring instruments, anindicating ammeter 20 and a curve drawing ammeter 21 being illustrated.Gonnected to the upper end of casing 3 is a pipe 22. In use, pipe 22 isconnected to the chamher in which the vacuum is to be measured, pipesection 18 being open-to atmosphere. Now, as the vacuum increases,atmospheric pressure acting on the surface of the liquid in the open endof pipe section 18 will force the mercury down pipe sections 18 and 17and up in casing 3, thereby increasing the roe depth of the mercury ringsurrounding the middle leg of the transformer core. This causes anincrease in the current flowing in the primary winding which increase incurrent will be proportional to the increase in the depth of the mercuryring, and since the depth of the mercury ring is proportional to thedegree of vacuum, it follows, therefore,

that the current flowing in the circuit comprising lead wires 13 and 1%and transformer winding 7 will be proportional to the vacuum. nstruments2-0 and 21 may be calibrated in terms of inches of mercury vacuum, interms of absolute pressure or other suitable terms, and as the vacuumvaries, causing the mercury ring in casing '3 to rise and fall, theseinstruments will measure continuo-usly the value of the vacuum.

- The pipe 16 and the pipe comprising pipe sections 17 and 18 shouldhave a length such that when the mercury is in Zero position, a columnof mercury about 30 inches high will be established in pipe sections 17and 18. The instrument then will be capable of measuring the highestvacuum met with in ordinary commercial practice.

In a great many applications, such as, for example, in measuring thevacuum in turbine condensers, there is little interest in indica ing ormeasuring accurately vacuums of low value, the thing oat primaryimportance being to measure the vacuum when of higher value, the vacuumbeing of higher value all the time except when starting up. The scaledeflection of an indicating ammeter, such as that indicated at 20, isnecessarily limited, and for this reason it is desirable to use the major portion or" the available scale space for indicating thehigher-vacuum values so that the unit scale markings may be wideapartand easily read. It is for this reason that pipe section 17 madeofrelatively large diameter and pipe section 18 of relatively smalldiameter. \Vith .the arrangement shown it will be clear that the initialdeflection of the mercury, i. e. the deflection which takes place inpipe section 18, will efiect but a relatively small rise in the mercuryin casing 3 and hence but a small increase in the current flowingthrough the indicating instruments. Hence this part of the deflectionwill cover but a. small partof the scale oi the indicating instrument.Now, when the deflection begins to take place in pipe section 17 .a muchlarger volume of mercury will be displaced so that the rise oi themercury in casing 3 will be much more rapid, thus more rapidlyincreasing the rate of flow of current through the indicatinginstruments. For example, the deflection in pipe section 18 mayrepresent vacuum from zero inches of mercury to twenty inches ofmercury, and that in pipe section 17 from twenty inches of mercurytothirty inches of mercury. It will be understood that any suitablerelative which indicates the vacuum on ordinary elecdiameters for pipes17 and 18 may be used to take care of the conditions met with in anyparticular instance, and also that the one leg may comprise sections ofmore than two diameters. In any event, the indicating instruments wilhare scale markings to conform to the a'rangement in any particularcase.

By my invention, Iprovide a vacuum gauge trical indicating instrumentsand'these instruments may be placed at any suitable point or pointsdesired. Also it will be clear by using what may be termed the leadingleg of the U-tube, pipe sections of different relative diameters, I-amenabled to utilize the major portion of the scale of an indicatinginstrument for a relatively small portionot the range of the quantitytobe indicated, thereby enabling large easily read markings to beprovided on the instrument.

In accordance with the provisions of the patent statutes, 1 havedescribed the principle of operation of my invention, together with theapparatus which I now consider to represent the best embodiment thereof,but I desire to have it understood that the apparatus shown is onlyillustrative and that the invention may be carried out by other means.

What I claim as new and desire to secure :by Letters Patent of theUnited States is i 1. In an instrument of the character-described, aU-tuloe having'two legs and indicating liquid in said legs, one of saidlegs comprising a lower section of relatively large diameter andan'u'pper section of small diameter, and theother of said legs having aportion of large diameter in line with the upper end of the uppersection-of the first referred to leg, said upper section of the firstreferred to leg being so small in diameter compared to the diameter ofthe upper portion of the other leg that when the liquid in such uppersection of the first referred to leg is forced downward it affects tobut a limited extent the level of the liquid in such other leg, andindicating means actuated by the level of the liquid in the upperportion of such other leg.

' 2. In an instrument of thecharacter described, the combination of acasing, a pipe of small diameter connected to the bottom of said casing,said casing and pipe forming one leg of a U-tube', a second casingadjacent the lower portion of said pipe and connected thereto, apipe ofsmall diameter connected to the top of said second casing, said secondcasing and pipe forming the otherleg of the U-tube, said second-namedpipe being of a diameter so small compared to the diameter of thefirst-named casing that when indicating 1 liquid is forced out of it, itafiects to but a limited extent the'level of the liquidin saidfirst-named casing. I

3. A U-tube comprising two adjacent parallel logs, the upper portion ofone of said legs being of relatively large diameter, indicating liquidin said U-tube, and means associated with said portion or" relativelylarge diameter for indicating the liquid level therein, the upperportion of said other leg being small com pared to its remaining portionand to said portion of relatively large diameter whereby the initialdeflection of the liquid in said other leg afiects to but a limitedextent the liquid level in the one leg.

In witness whereof, I have hereunto set my hand this 12th day ofSeptember, 1924.

REW E. WOOLLEY.

